Acyline is a novel GnRH antagonist found in animal studies to be a potent
suppressor of circulating gonadotropin and testosterone (T) levels. We
conducted the first study of acyline administration to humans. Eight
healthy, eugonadal young men were administered a series of acyline
injections (0, 2.5, 7.5, 25, and 75 microg/kg), each injection separated
by at least 10 d. Serum FSH, LH, and T levels were measured for 7 d after
injections. Acyline suppressed FSH, LH, and T levels in a dose-dependent
fashion. Maximal suppression occurred after injection of 75 microg/kg
acyline, which suppressed FSH to 46.9 +/- 2.5%, LH to 12.4 +/- 2.2%, and T
to 13.4 +/- 1.4% of baseline levels, maintaining suppression for over 48
h. Serum acyline levels peaked at 1 h at 18.9 +/- 0.9 ng/ml, remained
significantly elevated above background 7 d after injection, and returned
to background levels by 14-17 d after injection. Side-effects at the site
of injection were limited to infrequent blush and pruritus that resolved
within 90 min of injection. Higher doses of acyline might be effective as
depot injections for long-lasting gonadotropin suppression in
hormone-dependent diseases and for use in male hormonal contraception
regimens.

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Endocrine Society

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male contraception

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andrology

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5-alpha reductase inhibitors

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testosterone

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gonadotropins

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Safety

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Research Support, U.S. Gov't, P.H.S.

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Testosterone, blood

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Skin, drug effects

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Humans

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Adult

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Oligopeptides, adverse effects, blood, pharmacology

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Pruritus, chemically induced

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Male

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Gonadorelin, antagonists & inhibitors

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Gonadotropins, blood

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Acyline: the first study in humans of a potent, new gonadotropin-releasing hormone antagonist